The present invention relates to a substrate processing method and a substrate processing device, for processing the surface of a substrate used for the manufacture of a semiconductor device.
These days, in the semiconductor manufacturing process, the contamination of the surface of a substrate with an organic material (especially, a non-volatile organic material) is focused as a problem. More specifically, it is recently known that when a film forming process, for example, a process of forming a gate oxide film is carried out with an organic matter present on the surface of the substrate, the withstand voltage of the gate oxide film thus obtained is deteriorated.
Conventionally, there are several methods of preventing the contamination of the surface of a substrate with an organic matter, that is, a method of managing the time period of leaving the substrate outside (in a predetermined atmosphere) between processing steps, a method of housing the substrate in a box (miniature environment) or a stock container, having a predetermined atmosphere (for example, nitrogen gas atmosphere or degasified atmosphere), and a method of removing organic matters by a chemical filter from the atmosphere to which the substrate is exposed.
As the integration of semiconductor devices becomes high, the quality of each film in the semiconductor device is considered as being more important, and it becomes necessary to accurately remove organic matters. However, with the above-listed methods, it is not possible to fully prevent the contamination of a substrate with an organic matter, under the present status. Therefore, there has been a demand for a more certain method or means capable of preventing the contamination of a substrate with an organic matter.
The object of the present invention is to provide a substrate cleaning method and a substrate cleaning device, which are capable of effectively preventing the attachment of an organic matter on the surface of a substrate placed in a processing atmosphere, and maintaining the surface in a clean state such that the quality of a film formed thereon is not degraded.
The inventors of the present invention focused on the behavior of organic matters, that is, the adsorption to and detachment from a substrate within a clean room atmosphere, in the process of manufacturing semiconductor devices, and have found out that the behavior of the organic matters, that is, the adsorption and detachment, varies due to the difference in the absorption heat of an organic matter with respect to the substrate. Further, the inventors have found that the adsorption amount of organic matters differs between the cases where the surface of the substrate is hydrophilic and where it is hydrophobic. The present invention is based on these findings.
According to the present invention, there is provided a substrate processing method of processing a surface of a substrate in manufacture of a semiconductor device, characterized by comprising:
(a) a surface processing step for making a substance having an adsorption heat higher than that of an organic matter whose adsorption on the surface of the substrate, which has been cleaned, is undesirable, adsorbed on the surface of the substrate; and
(b) a film formation step for forming a thin film on the surface of the substrate which was processed in the step (a).
In this case, it is preferable that in the step (a), a substance having an adsorption heat higher than that of dioctyl phthalate should be adsorbed on the surface of the substrate. Further, in the step (a), it is preferable that an organic compound of aliphatic hydrocarbons, excluding aromatic hydrocarbons, should be adsorbed on the surface of the substrate, and it is most preferable that triacontane should be adsorbed on the surface of the substrate. It should be noted that in the present invention the surface of the substrate is hydrophobic in many cases.
Further, it is preferable that after the step (b), the substance of the above step (a) should be adsorbed on the surface of the substrate, on which the film was formed. In this manner, harmful non-volatile organic matters for a film-formed surface such as a heat oxide film, are not adsorbed, and therefore it is very advantageous for the process to be carried out in a later step.
Further, it is preferable that before the step (a), the surface of the substrate should be subjected to a cleaning process, so as to remove organic matters from the surface of the substrate. In this case, it is preferable that the surface of the substrate is cleaned by a dry-type cleaning method or by a wet-type cleaning method. As the dry-type cleaning method, it is preferable that the ultraviolet ray irradiated ozone cleaning method should be employed. Further, as the wet-type cleaning method, it is preferable that a combination of a scrubbing method and mega-sonic method should be employed.
According to the present invention, a substance having an adsorption heat higher than that of an organic matter which should not be adsorbed on the surface of a substrate, which has been cleaned, is made adsorbed on the surface of the substrate, and therefore non-volatile organic matters which are harmful for the manufacture of a semiconductor device are not adsorbed on the surface of the substrate. Since such a surface processing substance is not easily desorbed from the surface of the substrate, its effect can be maintained for a long period of time. Further, such a surface processing substance is easily adsorbed on the surface of a substrate, it can be easily adsorbed on the surface of the substrate by a short-time process. Therefore, the film forming process can be carried out in the state that harmful non-volatile organic matters are not present on the surface of the substrate, thus remarkably improving the yield of the process.
According to the present invention, there is further provided a substrate processing method of processing a surface of a substrate in manufacture of a semiconductor device, characterized by comprising:
(A) a surface processing step for making a substance containing a hydroxy group or a ketone group, adsorbed on the surface of the substrate; and
(B) a film formation step for forming a thin, film on the surface of the substrate which was processed in the step (A).
In this case, it is preferable that in the step (A), an organic compound of aliphatic hydrocarbons, except for the aromatic hydrocarbons, should be adsorbed on the surface of the substrate, and one or more organic compounds selected from the group consisting of isopropyl alcohol, 2-ethylhexanol, methyl alcohol and ethyl alcohol should be adsorbed on the surface of the substrate. It should be noted that in the present invention, the surface of the substrate is hydrophobic in many cases.
Further, it is preferable that after the step (B), the substance of the step (A) should be adsorbed on the surface of the substrate, on which the film was formed.
Furthermore, it is preferable that before the step (A), the surface of the substrate should be subjected to a cleaning process, so as to remove organic matters from the surface of the substrate. In this case, it is preferable that before the step (A), the surface of the substrate should be cleaned by a dry-type cleaning method or by a wet-type cleaning method. As the dry-type cleaning method, it is preferable that the ultraviolet ray irradiated ozone cleaning method should be employed. Further, as the wet-type cleaning method, it is preferable that a combination of a scrubbing method and mega-sonic method should be employed.
According to the present invention, a substance containing a hydroxy group or a ketone group is made adsorbed on the surface of the substrate, and therefore non-volatile organic matters which are harmful for the manufacture of a semiconductor device are not substantially adsorbed on the surface of the substrate. For example, when the substrate is subjected to a process with an HF (hydrogen fluoride), the surface becomes hydrophobic. To the hydrophobic surface, a much lower amount of harmful organic matter is adsorbed than to a hydrophlic surface, although it is never absent. Therefore, by attaching a substance containing a hydroxy group which is compatible with the hydrophobic surface, to the surface of the substrate, the adsorption of non-volatile organic matters which are present in the air can be avoided. Thus, the film formation process can be carried out on the surface of the substrate in the absence of non-volatile organic matters, and therefore it is possible to form a film exhibiting excellent characteristics, on a substrate.
According to the present invention, there is provided a substrate processing device for processing a surface of a substrate in manufacture of a semiconductor device, characterized by comprising: surface processing means for making a substance having an adsorption heat higher than that of an organic matter whose adsorption on the surface of the substrate, which has been cleaned, is undesirable, and/or a substance containing a hydroxy group or a ketone group, adsorbed on the surface of the substrate.
In this case, it is preferable that the surface processing means should make an organic compound of aliphatic hydrocarbons having an adsorption heat higher than that of dioctyl phthalate, adsorbed on the surface of the substrate, and it is most preferable that the surface processing means makes one or more of tricontane, isopropyl alcohol, 2-ethylhexanol, methyl alcohol and ethyl alcohol should be adsorbed on the surface of the substrate.
Further, it is preferable that the surface processing means should include heating means for directly or indirectly heating the substrate.
Furthermore, it is preferable that the substrate processing device should further comprise a plurality of processing vessels each containing a processing liquid for processing a substrate, and a transfer mechanism for transfer the substrate to load it in the processing vessel, wherein at least one of the processing vessel should contain a solution of the substance having a high adsorption heat, and the at least one processing vessel should serve as the surface processing means.
It is preferable that the processing vessel serving as the surface processing means should include means for immersing a substrate in the processing liquid. Thus, it becomes possible to attach a substance having a high adsorption heat or containing a hydroxy group, onto the surface of a substrate, surely without having unevenness.
Moreover, it is preferable that the processing vessel serving as the surface processing means should include means for spraying the processing liquid onto a substrate. Furthermore, it is preferable that the processing vessel serving as the surface processing means should include means for introducing a substrate in a gaseous processing liquid atmosphere. By employing the structure for spraying the solution liquid onto a substrate or the structure for introducing a substrate in a gaseous processing liquid atmosphere, the contact time periods in which the processing solution contacts the entire surface of the substrate become substantially the same, and therefore it becomes possible to attach a substance having a high adsorption heat and containing a hydroxy group, uniformly on the surface of the substrate. It should be noted that the processing liquid here means a solution of a substance having a high adsorption heat or a substance containing a hydroxy group or a ketone group.
Further, it is preferable that the processing vessel serving as the surface processing means is a chemical liquid vessel situated at the last stage. With this structure, it becomes possible to shorten the time period in which a substrate is exposed to the air up until the film formation process, after attaching a substance having a high adsorption heat or a substance containing a hydroxy group or a ketone group, uniformly to the surface of the substrate, and therefore the adsorption of non-volatile organic matters which cause an adverse influence on the film formation process, can be effectively prevented.